Looking to automate a duct work blastgate

[ADWSystems]

I am looking for some options for the mechanical side of automating a duct work blast gate. This is one of the actual blast gates, typically used in woodworking but also elsewhere. The gate slides approximately 4" for the one pictured, but I'd like to keep the design scalable to do 5" and 6" as well.

Blast Gate Photo

I have much of the control and interface designed, but I'm looking for solutions for the mechanical side (the simpler the better)

So far I have come up with the following ideas:
1. Pneumatic cylinder with a matching throw (4, 5, or 6 inches)
2. Solenoid, pneumatic cylinder, or automotive door lock actuator. These all have short throws, but a lever arm the proper length throw could be achieved.
3. Whatever you guys come up with.

I was watching TV and saw a train drive wheel and got another idea. A motor with an arm the correct length and attach it to the lip (facing down and away in the picture). The end attached to the gate would be able slide because arm would swing an arc (not travel linear like the gate will). I'm figuring on a DC motor (because it would have to be reversible) and rotating the motor only 90 degrees. I'm stuck on figuring out how to limit the motor's travel and when to stop the motor. Any ideas? All suggestions are welcome.

P.S. Please keep in mind I'm trying to keep this cheap and use parts that are readily accessible.

 

[Mike_2545]

A 1" pneumatic cylinder with a lever arm of the appropriate length would work, you can scale it to match the size of your application...

 

[3v0]

If you are willing to go pneumatic then think about using air shocks from cars. A few hours in a decent junk yard may provide enough to outfit the shop. Or Not.

3v0

 

[user_88]

A stepper motor, a length of acme threaded rod, and the corresponding acme nut would probably do what you want. I used this setup to open and close a 3" dia. sliding gate sewage type valve. .....
However, I will have to dig it out of the spare parts box to get a photo.
If you are worried about programming, there is a programmer called Basic Stamp, that just uses a few commands ... very simple ... to control the pulses to the stepper controller IC, as well as the direction.

 

[Boncuk]

How about that?

Open - spring loaded, close using a camshaft.

Using a double sided pneumatic cylinder you'd just have to use a limit switch for the small size doors.

Check out Festo pneumatic for small pneumatic cylinders.

Boncuk

 

[ADWSystems]

So far good ideas, but most covering the same terrain. I can get both the correct length and short throw pnuematic cylinders. I'm holding that option because I'd prefer not to be tied to having to run the air compressor to make the system work, plus I'd also have to run a pair of air lines or an airline and pair of wires to each gate to make the system work. A strictly electromechanical option with running only two wires to each gate sounds better to me.

It's preferrable to keep the system non-programmable, or at worst case limited to a 16v8 or 22v10 type PLD.

Along the lines of the threaded rod actuator, why a stepper motor? Why not just a regular reversible DC motor?

I'm liking the cam idea, but not the spring loaded part. The cam is very much along the lines of the thoughts of the "train wheel" analogy I was trying to present. If the gate had a pin sticking out, it could ride in a groove on circular plate affixed to a motor. That configuration is actually a cam and has a specific name, internal roller cam if I'm not mistaken. Depending on the configuration of the groove, the motor would need to rotate a specific distance to open and close. I had proposed 90 degrees and then reverse, but it could rotate 180 and stop to open and then 180 the same direction to close.

I did some sketching of the 180 degree option, the cam would be a circular groove 4" in diameter (plus the pin diameter), offset half way from the motor pin.

The 90 degree option is harder to picture. The groove would be 90 degrees of an 8" diameter circle. The starting point of the groove would be near the center of the plate near the motor and spiral out towards the edge over the course of 90 degrees. The spiral is just really a 90 degree arc of an 8" diamater circle (to give 4" of linear travel in 90 degrees of rotation)

I still need a way to stop a DC motor after it turns a specific amount. Any thoughts?

 

[stevez]

Have a look at Belimo websites. They (and many others) manufacture damper and valve operators. I am thinking less that you purchase what you want and more that you use the research for ideas.

 

[Boncuk]

If you can mount a small magnet to the door a TLE4905 would serve as a limit detector. It is easy to use and to interface with any circuit you design.

Additionally it's easy to work with since it is a through hole device.

If you consider using a cam I suggest to make it a way the door is fully open at 180 degrees and fully closed at 360 (0) degrees. That way you might save the circuitry to reverse motor direction.

Boncuk

 

[user_88]

Along the lines of the threaded rod actuator, why a stepper motor? Why not just a regular reversible DC motor?

With a stepper motor and its associated controller, you would not require any limit switches. Just specify the number or steps to take to get the corresponding gate/blade displacement. Furthermore, the direction of movement of the stepper is determined by a single high/low bit control on the stepper motor controller.

The stepper motor would not have the high torque capability of the pneumatic cylinder, or the DC motor. However, if the torque/force requirement is not too great, a reasonably sized stepper motor would probably have enough strength to do the job.

 

[ADWSystems]

Interesting. I have not seen a stepper controller that has an input in terms of step count. I have only seen pulse-input (you send a pulse and it figures out what to pulse to take the next step) and steady run input controllers (ones that run until you tell them not to).

 

[user_88]

Sorry about the misunderstanding.... you are correct about the pulse input.
The number of pulses/steps is determined by a program within the basic stamp
µcontroller, and the motor direction is controlled by a hi/lo pin on an Allegro stepper motor controller integrated circuit.

I will try to post a picture and some details later, if I can find the parts.

 

[ADWSystems]

Don't worry about that. I know how steppers work, I was hoping that you had something I didn't know about. The other problem would be making sure that the stepper actually made it to the right position without missing a step.

 

[shortbus=]

Here is a actuator All Electronics | Electronic and Electro-Mechanical Parts and Supplies at Discount Prices

It works on 12VDC two wires, you reverse polarity to reverse the direction. It is motor driven and stops automatically and holds in each direction. Uses no current except when moving.

They are door lock actuators from a GM car. They should move the blast gate for you. You could get one from a junk yard locally to try it.

 

[ADWSystems]

I have one of those. The actuator end is just plastic and snapped off when I tried to use it. The rod that goes through it is L-shaped and when I applied power, the rod twisted and snapped the end off. It's still an option is I can find a U-shaped piece to hook to the end that would avoid the torque and twist that broke the first one.

That actuator brings up a good point though. It looks like it's a motor and something. Maybe spur and rack gears? How does that actuator stop when it reaches the end?

 

[shortbus=]

That actuator brings up a good point though. It looks like it's a motor and something. Maybe spur and rack gears? How does that actuator stop when it reaches the end?

Yes it's a rack and pinon. I think it just hits stops on both ends of travel. they move pretty fast so just a 555 monostable circuit would work to open and close.